The production of a highly integrated semiconductor element generally has a series of processes as follows: a conductive thin film such as a metal film as a conductive wiring material and an interlayer dielectric film for insulation between conductive thin films are formed on an element such as a silicon wafer; after that, a photoresist is uniformly applied to the surface thereof to provide a photosensitive layer, and this is subjected to the selective exposure/development treatment to form a desired photoresist pattern; then the dry etching treatment is applied to the interlayer dielectric film using the photoresist pattern as a mask to form a desired pattern on the thin film; and then the photoresist pattern, residue generated by the dry etching treatment (hereinafter referred to as “dry etching residue”), etc. are completely removed by ashing with oxygen plasma, cleaning with a cleaning solution or the like.
Recently, the miniaturization of design rules has been accelerated, and the limit of high-speed arithmetic processing has been gradually controlled by signal transmission delay. For this reason, the conductive wiring material has been changed from aluminium to copper which has lower electrical resistance, and the interlayer dielectric film has been changed from a silicone oxide film to a low dielectric constant film (a film having a dielectric constant of less than 3, hereinafter referred to as “low-k film”). Adhesion of copper to the interlayer dielectric film is insufficient, and when copper is brought into contact with the interlayer dielectric film, copper is dispersed in the interlayer dielectric film over time. In order to improve these matters, a method for inserting a film made of a material containing tantalum which is called a “barrier metal” between copper and the interlayer dielectric film is generally employed. In addition, with the miniaturization of design rules, the constitution of the gate of the transistor has been gradually changed from a combination of silicon oxide and polycrystalline silicon to a combination of a high dielectric constant material and a metal. There is a case where a tantalum-containing material is used as this metal.
When a photoresist and dry etching residue are removed with oxygen plasma, there is a problem that a low-k film is damaged due to exposure to oxygen plasma or the like, resulting in significant deterioration of electrical characteristics. In addition, the tantalum-containing material is damaged due to exposure to oxygen plasma or the like, resulting in problems in production processes after that. For this reason, in the production of a semiconductor element using a low-k film and a tantalum-containing material (FIG. 1), it is desired to suppress damage to the low-k film and the tantalum-containing material while removing a photoresist and dry etching residue at a level comparable to that of an oxygen plasma process.
Regarding the treatment with a cleaning solution, it is known that a photoresist and dry etching residue can be removed by using a hydrogen peroxide-containing strong alkaline cleaning solution. The hydrogen peroxide-containing strong alkaline cleaning solution is excellent in removability of the photoresist and dry etching residue, but when the cleaning solution is brought into contact with a tantalum-containing material, it is significantly damaged. Under such circumstances, it is desired to develop a hydrogen peroxide-containing strong alkaline cleaning solution capable of effectively removing a photoresist and dry etching residue without damage to a tantalum-containing material and a cleaning method using the same.
Patent Document 1 proposes a wiring forming method using a cleaning solution containing an alkali and WzMXy (in the formula: M represents a metal selected from the group consisting of Si, Ge, Sn, Pt, P, B, Au, Ir, Os, Cr, Ti, Zr, Rh, Ru and Sb; X represents a halide selected from the group consisting of F, Cl, Br and I; W is selected from H, an alkali or alkaline earth metal, and a metal-ion-free hydroxide base moiety; y represents a number of from 4 to 6 depending on a metal halide; and z represents a number of 1, 2 or 3). By the cleaning method described in Patent Document 1, a photoresist cannot be removed, and damage to a low-k film cannot be suppressed. Therefore, it cannot be used for the above-described purpose (see Comparative Example 8). Further, a cleaning solution, in which WzMXy described in Patent Document 1 is blended in the cleaning solution to be used in the cleaning method of the present invention instead of the alkaline earth metal compound that is blended for the purpose of suppressing damage to the tantalum-containing material, damages the tantalum-containing material and the low-k film (see Comparative Example 9).